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SGLang & The Engine Landscape

🔧 SGLang & Alternative Engines12 min125 BASE XP

SGLang: RadixAttention

SGLang takes a different approach to KV cache management using a radix tree data structure.

RadixAttention Explained

Instead of vLLM's block-based paging, SGLang organizes KV cache in a radix tree (trie) that automatically discovers and reuses shared prefixes across requests — no manual configuration needed.

FeaturevLLM (PagedAttention)SGLang (RadixAttention)
Cache StrategyBlock-based virtual memoryRadix tree prefix sharing
Best ForHigh-throughput, diverse requestsPrefix-heavy workloads (RAG, multi-turn, agents)
SpeedupBaseline10-20%+ on prefix-heavy workloads
ConfigManual prefix caching setupAutomatic prefix detection

When To Use What

EngineBest Use CaseHardware
OllamaLocal dev, single user, prototypingAny (CPU/GPU)
llama.cppCPU inference, edge, hybrid GPU/CPU, max flexibilityUniversal
vLLMProduction multi-user GPU servingNVIDIA GPUs
SGLangRAG, multi-turn chat, agentic workloadsNVIDIA GPUs
TensorRT-LLMMaximum throughput on NVIDIA hardwareNVIDIA (Hopper+)
ExLlamaV2Fastest single-user local inferenceHigh-end NVIDIA
💡 Rule of Thumb: Start with Ollama for prototyping → graduate to vLLM/SGLang for production → consider TensorRT-LLM only if you need absolute maximum throughput on NVIDIA hardware.
KNOWLEDGE CHECK
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What data structure does SGLang use for KV cache management?
Hash table
Linked list
Radix tree (trie)
B-tree
Watch: 139x Rust Speedup
SGLang & The Engine Landscape | SGLang & Alternative Engines — Open Source AI Academy